A. Field of the Invention
This invention relates generally to the field of biological sample testing apparatus and systems, and more particularly to the subject of test sample cards which have one or more wells for containing a fluid or test sample containing a microbiological agent (such as a microorganism) and a reagent, and in which the fluid or test sample is introduced into the card via a straw-like tube known in the art as a transfer tube.
B. Description of Related Art
A variety of test sample cards are described in the patent literature which have a well or reaction site for receiving a fluid sample containing a microbiological agent, such as a microorganism, and a reagent. Several representative patents include Meyer et al., U.S. Pat. No. 4,318,994, Charles et al., U.S. Pat. No. 4,116,775; Fadler et al., U.S. Pat. No. 4,038,151 and Charles et al., U.S. Pat. No. 4,118,280, the contents of each of which are fully incorporated by reference herein. These patents describe a test sample card having a plurality of wells arranged in the test sample card body. The reagent is typically loaded in the wells of the card during the completion of manufacture of the card. The reagent typically comprises a growth medium for a microbiological agent in a fluid or test sample. It is known to load a different reagent in each of the wells of the card in order to perform identification testing of a fluid sample containing an unknown microbiological agent or organism. It is also known to use the cards to test the microbiological agent for susceptibility to the antibiotics by loading various antibiotic reagents into the wells.
In the sample testing system described in the Charles et al '280 patent, after the well of the test sample card has been loaded with the fluid sample, the card is incubated for a period of time to promote a reaction between the microorganism and the reagent, i.e., growth of the microorganism. After a period of time, the well is subject to optical analysis by a transmittance light source and a detector which are positioned on opposite sides of the well or by alternate detection methods. If the growth medium or reagent is specifically suited for or "matches up" with the particular microorganism in the fluid sample, the population of the microorganism increases substantially, or some other predetermined reaction, i.e., chemical reaction, takes place, which results in the well turning cloudy and thus having a change in light transmission characteristics. The detector determines the amount of light that is transmitted from the source through the well. By comparing the transmittance measurement over a period of time, typically several hours at least, with an initial transmittance measurement, it is possible to determine whether in fact the reagent and microbiological agent are matched by virtue of the change in transmittance measurement reaching a threshold value, such as 25 or 30 percent. The change in light transmission characteristics therefore can be used to indicate the presence of a specific microorganism in the well. Identification and susceptibility may also be detected by absorbency measurements where a fluorescent agent is provided in the growth medium.
It is known in the art to introduce the fluid sample into the test sample card using a transfer tube and vacuum techniques. One end of the straw-like transfer tube is inserted into an intake port in the test sample card. Typically, this is performed manually by a laboratory technician at the time the test sample card is used. The free end of the transfer tube is then inserted into a receptacle, such as a test tube, that contains the fluid sample. The test tube/fluid sample with transfer tube and test sample card are then placed as a unit within a vacuum chamber. Vacuum is drawn in the chamber and then released. The release of vacuum draws fluid from the receptacle into the fluid passages and wells, loading the wells with fluid.
The present inventors has appreciated that problems have arisen with regards to prior art test sample card and transfer tube arrangements, in that the user may fail to adequately or properly install the transfer tube into the test sample card. When the transfer tube is not properly installed in the card, a potential for air to leak around the transfer tube and into the fluid passages in the test sample card exists. The air is then carried by fluid distribution to the test sample wells, where the air forms small bubbles in the sample wells. Air bubbles in the wells can adversely affect the accuracy of the reading of the wells by the optical system. Thus, the inventors have appreciated that the manner in which the transfer tube is inserted into the test sample card is a important performance issue in terms of the ability of the card and associated optical instrument to perform up to their optimal capability.
The present invention solves the problem of inadequate transfer tube connection to the test sample card and resulting leakage of air into the fluid distribution channels by providing a novel locking arrangement in the test sample card fluid port that insures that the technician has properly inserted the transfer tube into the test sample card.
It is therefore a primary object of the invention to provide a test sample card and transfer tube arrangement that achieves a positive, leak-free, locking engagement between the transfer tube and the test sample card fluid port, thereby ensuring optimal performance of the test sample card and optical reading system.
A second object of the invention is to provide a locking feature in a test sample card that is easy to use by the technician, and enables the technician to install the transfer tube into the test sample card and immediately know, by both visual and tactile means, whether the transfer tube has been correctly and completely installed in the test sample card.